I broke in the D5 "NOT" according to the instruction. I kept the engine running "Very" rich for 1 litre on starter box. and another litre on the track with "Very" rich needle setting. and i start to lean the engine progressively. I inspected the conrod after the day and the conrod holds up perfectly. I finished 1 gallon of fuel and inspect the engine again and the conrod still hold up nicely and it is still difficult to remove the conrod/piston from the crankpin for rebuild.
It does happen to novarossi based engine on bad conrod. that is why the conrod has a copper busing there and this is the purpose to protect the crankpin. JMHO